Poultry is a major source of protein in the western diet. However, the result of many years of breeding selection for fast-growing chickens and turkeys has resulted in the production of commercial poultry strains which have increased fat deposits. Because of this increased fat content, some nutritionists no longer recommend poultry over trimmed red meat. In addition, four times as much feed is required to produce 1 gram of fat compared to 1 gram of muscle, and so this increased fat content also elevates production costs (notably, the cost of feed represents over half of the expense of raising poultry--696 for broiler chickens, 61% for turkeys). Accordingly, the ability to produce poultry with a lower fat content would have both health and economic benefits.
Growth Hormone-Releasing Hormone (GHRH or GRF) and Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) are two members of the glucagon superfamily of proteins. They are neuropeptides which, amongst other activities, stimulate the release of pituitary growth hormone (GH), the major growth hormone in animals. In human studies, recombinant GH has been shown to increase lean body mass and reduce fat content in elderly adults. By extrapolation, the regulation of GH in agricultural animals may be useful to control growth rates and body composition. Accordingly, there is much interest in GRF and PACAP, and a major focus of the ongoing research is the search for genes which encode these neuropeptides in agriculturally important animal species, including poultry.
Although rat and human GRF have been shown to stimulate GH release from chicken pituitary cells in vitro, a chicken GRF has not yet been reported. It is a goal of the present invention to provide neuropeptide gene sequences and peptide sequences which function to stimulate GH release in poultry.